Battery chargers utilizing an AC or DC electrical current to supply a controlled voltage to a battery are known in the art. Accidentally shorting the leads, or reversing the polarity of the leads may seriously damage the battery charger, or cause the electrolites in the battery to boil, damaging the battery. Protection circuits to prevent these events have been expensive, and often do not protect against both reversed polarity and shorted leads or an overload condition, while providing for a trickle charge to maintain batteries during storage, or between use as often needed for recreational vehicles, boats, battery storage, or the like.